Solid-state grow-lights for plant cultivation

ABSTRACT

There is provided a light emitting device, for example a grow-light, comprising: a first solid-state light source that generates blue light with a blue photon flux; and a second solid-state light source that generates red light with a red photon flux; wherein a ratio of the blue photon flux to red photon flux is from about 1:3 to about 3:1. It may be that the broadband blue light substantially matches at least one of: the absorption peak wavelength of chlorophyll-a; the absorption peak wavelength of chlorophyll-b; and the absorption peak wavelength of carotenoid.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation application of U.S.Continuation-In-Part bypass application Ser. No. 17/665,240, filed Feb.4, 2022, said U.S. Continuation-In-Part bypass is of PCT application No.PCT/US2022/014641, filed Jan. 31, 2022, which claims the benefit ofpriority to U.S. Provisional application No. 63/143,765, filed Jan. 29,2021, entitled “SOLID-STATE GROW-LIGHTS FOR PLANT CULTIVATION”, each ofwhich are hereby incorporated by reference in their entirety.

FIELD OF THE INVENTION

Embodiments of the invention concern solid-state, LED-based, grow-lights(light emitting devices) for plant cultivation and in particular,although not exclusively, to solid-state light sources for grow-lightsfor promoting photosynthesis and plant growth.

BACKGROUND OF THE INVENTION

Factors such as temperature, humidity, wind, carbon dioxide, root-zonetemperature, water, nutrients, and oxygen levels play an important rolein regulating and promoting plant growth. In addition, light intensity,light spectral composition, and duration of exposure to light play amajor role in the growth cycle of plants including plant growth/biomassby the process of photosynthesis, plant morphology (shape) by theprocess of photomorphogenesis, and flowering time by the process ofphotoperiodism.

Photosynthesis is the process of converting light energy into chemicalenergy by the absorption of light by photosynthetic pigments. Lightenergy is absorbed by green chlorophyll pigments inside chloroplastsconcentrated in leaf cells. There are two main types of chlorophyll,named chlorophyll-a (Chl-a) and chlorophyll-b (Chl-b). Bothchlorophyll-a and chlorophyll-b each have absorption peaks atwavelengths corresponding to blue and red light regions of the visiblespectrum. Light energy, which can be measured by photon flux density(PFD), plays a significant role in photosynthesis and effects growthrate and biomass. As well as chlorophyll pigments plants can alsocontain carotenoid (Caro) pigments, for example β-carotene, whichprovide photoprotection and play a role in the absorption of light forphotosynthesis. Caro pigments, for example β-carotene, have absorptionpeaks corresponding to blue and green light.

The spectral range (wavelength range) of solar radiation (sunlight) from400 nm to 700 nm that is used in the process of photosynthesis isreferred to as Photosynthetically Active Radiation (PAR). Previously,photons at shorter wavelengths are believed to be so energetic that theycan damage cells and tissues, but are mostly filtered out by the ozonelayer in the stratosphere. Photons at longer wavelengths were believednot to carry enough energy to allow photosynthesis to take place.However, current thinking now believes that far-red light (longer than680 nm) plays an important role in photosynthesis through what is knownas the Emerson Enhancement Effect in which there is a significantincrease in photosynthesis when a plant is simultaneously exposed tolight of wavelengths in both the deep red (about 680 nm) and in thefar-red regions of the spectrum.

Light spectral composition can be used to regulate plant morphologythrough a process of photomorphogenesis which is related to the plant'sresponse to the spectral composition of light—that is the distributionof power density with wavelength. In plants, crytochrome and phototropinphotoreceptors are responsible for regulating plant development based onthe photomorphogenic effects of light corresponding to UV-A, UV-B, andblue portions of the electromagnetic spectrum. Crytochromes are believedto help control seed and seedling development as well as transitioningfrom the vegetative to the flowering stage of development, whilephototropins are believed to control directional growth towards a bluelight source (phototroprism). Phytochrome photoreceptors have a strongabsorption in the red region (Type I—phytochrome P_(r)) and, in thefar-red region (Type II—phytochrome P_(FR)), are believed to beresponsible for regulating seed germination (photoblasty), the synthesisof chlorophyll and the timing of flowering. Controlling the spectralcomposition of light—in particular the ratio of the red to bluelight—used in the propagation of plants can be effective in regulatingthe morphology and even the color of certain genotypes of plants. Ingeneral, UV to blue light inhibits cell expansion resulting in reducedleaf expansion/stem elongation, while far-red light enhances leafexpansion/stem elongation. The photomorphogenesis response is highlydependent on plant species. For example, for leafy greens such asspinach or lettuce far red light increases leaf expansion while in mostother species (e.g. tomatoes) it encourages tall stem growth. Incontrast, the photosynthesis process that controls plant growth issubstantially invariant of plant species.

Further, as described, control of the duration of light exposure,“photoperiod control”, can be used to control the flowering times ofshort-day and long-day plants.

Lighting requirements for plant growth are different from those ofgeneral lighting for human sight. The human eye has three types ofphotoreceptors (L-cones, M-cones, S-cones) that are sensitive to red,green, and blue light, and the eyes detects the ratio of the intensityof light for each color. Accordingly, for general lighting, and toensure accurate color vision (color rendering), it is preferred thatwhite light has an intensity spectrum, intensity versus wavelength, thatresembles sunlight as closely as possible for wavelengths of light fromthe blue to red colors of the visible spectrum. In contrast, plantsconvert light energy (Photon flux) into chemical energy and aresensitive to photon flux at different wavelengths of the spectrum.

In contrast to the human eye, plants have different light receptors andcells to sense and process light with the metric of light quantity(intensity) being photon-based, Photosynthetic Photon Flux (PPF) withunits μmol/s. PPF is a measure of the Photosynthetically ActiveRadiation (PAR) of a light source. As described above, the ratio of thephoton flux can influence various parameters of the plant such asbiomass, morphology, nutrition content, taste and flowering time. Thus,by controlling the photon flux ratio, horticultural growers canselectively modify/optimize plant characteristics.

Based on the strong absorption of blue and red light by plants,LED-based grow-lights generate purple light comprising a combination ofa narrowband blue LED that generates blue light with a dominantwavelength of about 450 nm and full width at half maximum (FWHM) ofabout 20 nm or shorter, and a red LED (or red phosphor) that generatesred light with a dominant wavelength of about 660 nm. Work by McCree(McCree K. J., 1972. The action spectrum, absorptance and quantum yieldof photosynthesis in crop plants. Agric. Meteorol., 9: 191-216) suggestthat the green to yellow part of the visible spectrum may also play arole in photosynthesis rate. As a result, there is growing interest inwhite LED-based grow-lights. Typically, white grow-lights comprise aplurality of warm white and cool white LEDs together with a deep redLED.

The present invention concerns improvements relating to solid-state,LED-based, light emitting devices for grow-lights and in particular,although not exclusively, to improving solid-state light sources thatgenerate light in the blue to cyan region of the spectrum for regulatingand/or promoting photosynthesis and plant growth.

SUMMARY OF THE INVENTION

Embodiments of the invention concern light emitting devices(grow-lights) comprising solid-state light sources (LEDs) whose emissionspectrum in the blue to cyan region of the spectrum (about 400 nm to 520nm) is configured to promote photosynthesis and plant growth. Asdescribed below, both the relative photosynthetic response curves, PAS(Photosynthesis Action Spectrum) and McCree Curve, indicate that plantgrowth efficiency is not just photon intensity dependent but alsowavelength dependent in the blue to cyan region from 400 nm to 520 nmwhere plant absorption efficiency is greatest.

In accordance with the invention, the spectrum of light generated by thesolid-state source may comprise one or more blue light emissions withpeak emission wavelengths (from 420 nm to 495 nm) corresponding with thepeak absorption wavelengths of chlorophyll and/or carotenoid pigments topromote photosynthesis and plant growth. Since the chlorophyll-a pigmentis believed to play the most significant role in plant photosynthesis,the spectral composition of light generated by the solid-state lightsource may include at least a blue light emission with a peak emissionthat substantially matches the peak absorption wavelength (about 430 nm)of chlorophyll-a.

According to an aspect of the invention the solid-state light source cangenerate a narrowband blue light emission (FWHM less than 25 nm). It isbelieved that a narrowband emission can maximize photosynthetic energyabsorption and photosynthetic efficiency. The narrowband solid-statelight source can comprise a narrowband LED.

Studies indicate that while maximum photon absorption occurs at theabsorption peak wavelength of the pigment, maximum photosynthesis ratecan occur at wavelengths away from the absorption peak wavelength.According to another aspect of the invention the solid-state lightsource can generate a broadband blue light emission (FWHM from 30 nm to80 nm) which can increase photosynthesis rate.

In this patent specification, broadband blue light refers to blue lightwith a FWHM (Full Width at Half Maximum) of at least 30 nm, preferablyfrom about 40 nm to 80 nm. Broadband can also be used to denote blue tocyan light that is composed of a combination of at least two differentwavelength blue to cyan light emissions. Broadband blue to cyan lightcan be generated using a combination of narrowband blue to cyan lightemissions of two or more different wavelengths. The different wavelengthnarrowband blue to cyan light emissions can be generated in two ways:(i) using multiple individual blue to cyan narrowband LEDs of differentpeak emission wavelengths or (ii) a single broadband LED that generatesmultiple blue to cyan narrowband emissions using, for example, speciallydesigned multiple different quantum wells in its active region. Thus, abroadband blue to cyan solid-state light source can be constituted byone or more narrowband solid-state light sources; such as for example,LEDs or laser diodes, each of which “directly” generates narrowband blueto cyan light of different peak emission wavelengths from 400 nm to 530nm. Alternatively, a broadband blue to cyan solid-state light sourcealso encompasses a broadband blue solid-state light source; for example,a broadband blue LED such as an InGaN/GaN blue to cyan LED having anactive region that directly generates blue to cyan light emissions ofmultiple different wavelengths using different quantum wells in amultiple-quantum-well (MQW) structure. Broadband solid-state lightsources of the invention are to be contrasted with PhotoluminescenceConverted (PC) LEDs that utilize UV solid-state light sources (UV LEDs)and generate blue light indirectly through a process ofphotoluminescence wavelength conversion of UV light using a blue to cyanlight emitting photoluminescence material (phosphor). In other words,broadband blue to cyan solid-state light sources in accordance with theinvention do not utilize/include a photoluminescence material togenerate blue to cyan light.

According to a further aspect of the invention, the solid-state lightsource can generate full spectrum blue light whose spectral compositionat wavelengths in the blue to cyan region of the spectrum, morespecifically for wavelengths from 400 nm to 520 nm of thePhotosynthetically Active Radiation (PAR), has an emission maxima whoseintensity is substantially constant (varies less than about 25%) overthe blue to cyan region of the spectrum. Full spectrum blue light canhave a spectral composition that more closely matches (resembles)sunlight/daylight at wavelengths in the blue to cyan region of thespectrum. Full spectrum blue light can have a spectral composition thatsubstantially matches (resembles) the PAS or McCree relativephotosynthetic response curves. Full Spectrum Blue solid-state lightsources may comprise multiple, two or more, broadband solid-state lightsources.

The solid-state light sources in accordance with various aspects of theinvention can be used together with red light emitting LEDs or redphosphors that generate red light emissions with peak emissionwavelengths corresponding to the absorption peaks of Chlorophyllpigments in the red region of the absorption spectrum. The red lightemitting diode(s) may comprise Phosphor Converted Red LED (PC Red LED)that comprises a narrowband blue LED and red photoluminescence material.The light emitting device may further comprise a red LED or a redphotoluminescence material that generates far red light emission from680 nm to 780 nm. This can increase photosynthesis when used incombination with red light in the Photosynthetically Active Radiation(PAR)—400 nm to 700 nm through the Emerson Enhancement Effect. Thesolid-state light source can also be used with broadband yellow to greenemission phosphors for generating a broadband white spectrum inhorticultural applications.

As described herein, while the wavelength in the blue to cyan region ofthe spectrum is important for plant photosynthesis and propagation, therelative photon count (photon flux) of photons in the blue and redregions of the spectrum is another important factor.

In arrangements, the Blue photon count can be substantially equal to theRed photon count. The inventors have determined that a grow-light havinga spectrum comprising a substantially equal photon count of Blue photonsand Red photons can promote photosynthesis.

In other arrangements, the Blue photon count can be greater than the Redphoton count. The inventors have determined that a grow-light having aspectrum comprising a greater blue photon count than Red photon countcan promote propagation.

In yet further arrangements, the Red photon count can be greater thanBlue photon count. The inventors have determined that a grow-lighthaving a spectrum comprising a greater red photon count than Blue photoncount can promote flowering.

According to an aspect of the invention, there is provided a lightemitting device, for instance a grow-light, comprising: a broadband bluesolid-state light source that generates broadband blue light with a peakemission wavelength from 420 nm to 495 nm and a full width at halfmaximum of at least 30 nm. It may be that the broadband blue lightsubstantially matches at least one of: the absorption peak wavelength ofchlorophyll-a; the absorption peak wavelength of chlorophyll-b; and theabsorption peak wavelength of carotenoid.

It may be that the broadband blue solid-state light source generatesbroadband with a peak emission wavelength of at least one of: from 420nm to 450 nm; from 460 nm to 480 nm; and from 450 nm to 465 nm and 480nm to 495 nm.

It may be that broadband light emission with a peak emission wavelengthfrom 420 nm to 450 nm substantially matches the absorption peakwavelength of chlorophyll-a. It may be that broadband light emissionwith a peak emission wavelength from 460 nm to 480 nm substantiallymatches the absorption peak wavelength of chlorophyll b. It may be thatbroadband light emission with a peak emission wavelength from 450 nm to465 nm and 480 nm to 495 nm substantially matches the absorption peakwavelengths of carotenoid.

The light emitting device, for instance the grow-light, may furthercomprise a red solid-state light source or red photoluminescencematerial that generates red light with a peak emission wavelength from630 nm to 680 nm.

It may be that the broadband blue light has a blue photon flux, and thered light has a red photon flux, and wherein a ratio of the blue photonflux to the red photon flux is from about 1:3 to about 3:1.

It may be that the ratio of the blue photon flux to the red photon fluxis about 1:1. It will be understood that “about” in the sense of said1:1 ratio may correspond to approximately ±0.3. Hence, it will beunderstood that the ratio of about 1:1 encompasses ratios from 0.7:1 to1.3:1. The inventors have determined that a grow-light having a spectrumcomprising a substantially equal photon count of Blue photons and Redphotons can promote photosynthesis.

It may be that the ratio of the blue photon flux to the red photon fluxis about 3:1. It will be understood that “about” in the sense of said3:1 ratio may correspond to approximately ±0.5. Hence, it will beunderstood that the ratio of about 3:1 encompasses ratios from 2.5:1 to3.5:1. The inventors have determined that a grow-light having a spectrumcomprising a greater blue photon count than Red photon count can promotepropagation.

It may be that the ratio of the blue photon flux to the red photon fluxis about 1:3. It will be understood that “about” in the sense of said1:3 ratio may correspond to approximately ±0.5. Hence, it will beunderstood that the ratio of about 1:3 encompasses ratios from 1:2.5 to1:3.5. The inventors have determined that a grow-light having a spectrumcomprising a greater red photon count than Blue photon count can promoteflowering.

It may be that the broadband blue light emission has a FWHM of one of:at least 40 nm; at least 50 nm; at least 60 nm; and from 40 nm to 80 nm.

It may be that the broadband blue solid-state light source generates afirst broadband blue light from 420 nm to 450 nm with a first bluephoton flux, and a second broadband blue light from 460 nm to 470 nmwith a second blue photon flux, and wherein a ratio of the first bluephoton flux to the second blue photon flux is from 2:1 to 4:1. In suchan arrangement, it will be understood that about 67% to 80% (about 75%)of the blue photon flux corresponds to the chlorophyll-a absorption peakand about 33% to 20% (about 25%) of the blue photon flux corresponds tothe chlorophyll-b absorption peak.

The light emitting device, for instance the grow-light, may furthercomprise an orange to red LED or orange to red photoluminescencematerial that generates an orange to red light emission with a peakemission wavelength from 630 nm to 680 nm.

The light emitting device, for instance the grow-light, may furthercomprise a far red solid-state light source or a far redphotoluminescence material that generates far red light with a peakemission wavelength from about 630 nm to about 780 nm. Such wavelengthsof light can increase photosynthesis through the Emerson EnhancementEffect.

It may be that the broadband blue solid-state light source comprises aplurality of narrowband blue LEDs for generating a plurality ofdifferent wavelength narrowband blue light emissions.

The broadband blue solid-state light source may comprise a broadband LEDhaving multiple different wavelength quantum wells that generatemultiple different wavelength narrowband blue light emissions.

Where the light emitting device is configured to generate white light,the light emitting device, for instance the grow-light, may furthercomprise a green to yellow photoluminescence material that generatesgreen to yellow light with a peak emission wavelength from about 540 nmto about 600 nm or a cyan to red photoluminescence material thatgenerates cyan to red light with a peak emission wavelength from about500 nm to about 680 nm.

It may be that the broadband blue solid-state light source generatesfull spectrum blue light from 400 nm to 520 nm with a spectrum whoseemission intensity varies by less than 25% over a wavelength range of atleast 40 nm.

It may be that the emission intensity varies by less than 20%, less than15%, or less than 10% over a wavelength range of at least 40 nm or lessthan 10% from 430 nm to 470 nm or from 450 nm to 465 nm.

According to another aspect, the invention comprehends a light emittingdevice, for instance a grow-light, comprising: a blue solid-state lightsource that generates blue light with a blue photon flux; and a redsolid-state light source that generates red light with a red photonflux; wherein a ratio of the blue photon flux to red photon flux is fromabout 1:3 to about 3:1.

It may be that the ratio of the blue photon flux to the red photon fluxis about 1:1. It will be understood that “about” in the sense of said1:1 ratio may correspond to approximately ±0.3. Hence, it will beunderstood that the ratio of about 1:1 encompasses ratios from 0.7:1 to1.3:1. The inventors have determined that a grow-light having a spectrumcomprising a substantially equal photon count of Blue photons and Redphotons can promote photosynthesis.

It may be that the ratio of the blue photon flux to the red photon fluxis about 3:1. It will be understood that “about” in the sense of said3:1 ratio may correspond to approximately ±0.5. Hence, it will beunderstood that the ratio of about 3:1 encompasses ratios from 2.5:1 to3.5:1. The inventors have determined that a grow-light having a spectrumcomprising a greater blue photon count than Red photon count can promotepropagation.

It may be that the ratio of the blue photon flux to the red photon fluxis about 1:3. It will be understood that “about” in the sense of said1:3 ratio may correspond to approximately ±0.5. Hence, it will beunderstood that the ratio of about 1:3 encompasses ratios from 1:2.5 to1:3.5. The inventors have determined that a grow-light having a spectrumcomprising a greater red photon count than Blue photon count can promoteflowering.

It may be that the blue solid-state light source comprises a broadbandblue solid-state light source that generates broadband blue light with apeak emission wavelength from 420 nm to 495 nm and a full width at halfmaximum of at least 30 nm.

The broadband blue solid-state light source may generate broadband witha peak emission wavelength of at least one of: from 420 nm to 450 nm;from 460 nm to 480 nm; and from 450 nm to 465 nm and 480 nm to 495 nm.

It may be that the broadband blue light substantially matches at leastone of: the absorption peak wavelength of chlorophyll-a; the absorptionpeak wavelength of chlorophyll-b; and the absorption peak wavelength ofcarotenoid.

It may be that the blue solid state light source generates a firstbroadband blue light from 420 nm to 450 nm with a first blue photonflux, and a second broadband blue light from 460 nm to 470 nm with asecond blue photon flux, and wherein a ratio of the first blue photonflux to the second blue photon flux is from 2:1 to 4:1. In such anarrangement, it will be understood that about 67% to 80% (about 75%) ofthe blue photon flux corresponds to the chlorophyll-a absorption peakand about 33% to 20% (about 25%) of the blue photon flux corresponds tothe chlorophyll-b absorption peak.

The red solid-state light source may comprise a narrowband blue LED anda red photoluminescence material.

The light emitting device, for instance the grow-light, may furthercomprise a far red solid-state light source or a far redphotoluminescence material that generates far red light with a peakemission wavelength from about 680 nm to about 780 nm.

According to another aspect, there is contemplated a grow-lightcomprising: a narrowband blue solid-state light source that generatesnarrowband blue light with a full width at half maximum from about 10 nmto 30 nm and a peak emission wavelength of at least one of: from 425 nmto 435; from 460 nm to 470 nm; and from 450 nm to 465 nm and 480 nm to495 nm.

The narrowband blue light may substantially match at least one of: theabsorption peak wavelength of chlorophyll-a; the absorption peakwavelength of chlorophyll-b; and the absorption peak wavelength ofcarotenoid.

It may be that the narrowband blue light source generates a firstnarrowband blue light from 420 nm to 450 nm with a first blue photonflux, and a second narrowband blue light from 460 nm to 470 nm with asecond blue photon flux, and wherein a ratio of the first blue photonflux to the second blue photon flux is about 3:1, that is from 2:1 to4:1. In such an arrangement, it will be understood that about 67% to 80%(about 75%) of the blue photon flux corresponds to the chlorophyll-aabsorption peak and about 33% to 20% (about 25%) of the blue photon fluxcorresponds to the chlorophyll-b absorption peak.

The light emitting device, for instance the grow-light, may furthercomprise a red solid-state light source or red photoluminescencematerial that generates red light with a peak emission wavelength from630 nm to 680 nm.

It may be that the narrowband blue light has a blue photon flux, and thered light has a red photon flux, and wherein a ratio of the blue photonflux to the red photon flux is from about 1:3 to about 3:1.

It may be that the ratio of the blue photon flux to the red photon fluxis about 1:1. It will be understood that “about” in the sense of said1:1 ratio may correspond to approximately ±0.3. Hence, it will beunderstood that the ratio of about 1:1 encompasses ratios from 0.7:1 to1.3:1. The inventors have determined that a grow-light having a spectrumcomprising a substantially equal photon count of Blue photons and Redphotons can promote photosynthesis.

It may be that the ratio of the blue photon flux to the red photon fluxis about 3:1. It will be understood that “about” in the sense of said3:1 ratio may correspond to approximately ±0.5. Hence, it will beunderstood that the ratio of about 3:1 encompasses ratios from 2.5:1 to3.5:1. The inventors have determined that a grow-light having a spectrumcomprising a greater blue photon count than Red photon count can promotepropagation.

It may be that the ratio of the blue photon flux to the red photon fluxis about 1:3. It will be understood that “about” in the sense of said1:3 ratio may correspond to approximately ±0.5. Hence, it will beunderstood that the ratio of about 1:3 encompasses ratios from 1:2.5 to1:3.5. The inventors have determined that a grow-light having a spectrumcomprising a greater red photon count than Blue photon count can promoteflowering.

The light emitting device, for instance the grow-light, may furthercomprise a far red solid-state light source or a far redphotoluminescence material that generates far red light with a peakemission wavelength from about 680 nm to about 780 nm. Such wavelengthsof light can increase photosynthesis through the Emerson EnhancementEffect.

The light emitting device, for instance the grow-light, may furthercomprise a green to yellow photoluminescence material that generatesgreen to yellow light with a peak emission wavelength from about 540 nmto about 600 nm.

The light emitting device, for instance the grow-light, may furthercomprise a cyan to red photoluminescence material that generates cyan tored light with a peak emission wavelength from about 500 nm to about 660nm.

According to another aspect of the invention, there is envisaged agrow-light comprising: a broadband full spectrum blue solid-state lightsource that generates a full spectrum blue light from 400 nm to 520 nmwith a spectrum whose emission intensity varies by less than 25% over awavelength range of at least 40 nm.

The emission intensity may vary by less than 20%, less than 15%, or lessthan 10% over a wavelength range of at least 40 nm.

It may be that the emission intensity varies by less than 10% from 430nm to 470 nm or from 450 nm to 465 nm.

It may be that the broadband full spectrum blue solid-state light sourcecomprises a plurality of broadband blue LEDs that each generate abroadband blue emission with a peak emission wavelength from 400 nm to520 nm.

The light emitting device, for instance the grow-light, may furthercomprise a red solid-state light source or red photoluminescencematerial that generates red light with a peak emission wavelength from630 nm to 700 nm.

It may be that the full spectrum blue light has a blue photon flux, andthe red light has a red photon flux, and wherein a ratio of the bluephoton flux to the red photon flux is from about 1:3 to about 3:1.

It may be that the ratio of the blue photon flux to the red photon fluxis about 1:1. It will be understood that “about” in the sense of said1:1 ratio may correspond to approximately ±0.3. Hence, it will beunderstood that the ratio of about 1:1 encompasses ratios from 0.7:1 to1.3:1. The inventors have determined that a grow-light having a spectrumcomprising a substantially equal photon count of Blue photons and Redphotons can promote photosynthesis.

It may be that the ratio of the blue photon flux to the red photon fluxis about 3:1. It will be understood that “about” in the sense of said3:1 ratio may correspond to approximately ±0.5. Hence, it will beunderstood that the ratio of about 3:1 encompasses ratios from 2.5:1 to3.5:1. The inventors have determined that a grow-light having a spectrumcomprising a greater blue photon count than Red photon count can promotepropagation.

It may be that the ratio of the blue photon flux to the red photon fluxis about 1:3. It will be understood that “about” in the sense of said1:3 ratio may correspond to approximately ±0.5. Hence, it will beunderstood that the ratio of about 1:3 encompasses ratios from 1:2.5 to1:3.5. The inventors have determined that a grow-light having a spectrumcomprising a greater red photon count than Blue photon count can promoteflowering.

The light emitting device, for instance the grow-light, may furthercomprise a far red solid-state light source or a far redphotoluminescence material that generates far red light with a peakemission wavelength from about 680 nm to about 780 nm. Such wavelengthsof light can increase photosynthesis through the Emerson EnhancementEffect.

The light emitting device, for instance the grow-light, may furthercomprise a green to yellow photoluminescence material that generatesgreen to yellow light with a peak emission wavelength from about 540 nmto about 600 nm.

The light emitting device, for instance the grow-light, may furthercomprise a cyan to red photoluminescence material that generates cyan tored light with a peak emission wavelength from about 500 nm to about 660nm.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects and features of the present invention willbecome apparent to those ordinarily skilled in the art upon review ofthe following description of specific embodiments of the invention inconjunction with the accompanying figures, in which:

FIG. 1A shows absorption spectra, absorption (%) versus wavelength (nm),for photosynthetic pigments: (i) chlorophyll-a (solid line—Ch1-a), (ii)chlorophyll-b (dotted line—Chl-b), and (iii) carotenoid (dashedline—Caro);

FIG. 1B is a Photosynthesis Action Spectrum (PAS), relativephotosynthetic response (%) versus wavelength (nm);

FIG. 1C is a McCree Curve, relative photosynthetic efficiency versuswavelength (nm);

FIGS. 2A and 2B are schematic views of a packaged light emitting devicein accordance with the invention in which FIG. 2A is a plan view of thedevice and FIG. 2B is a sectional side view through A-A;

FIG. 3 shows normalized absorption spectrum, normalized absorptionfactor versus wavelength (nm), for chlorophyll-a (dotted line—Ch1-a) andspectral power distribution, spectral power (W/nm) versus wavelength(nm), for (i) a narrowband blue solid-state light source Dev.1 (solidline—Dev.1) and (ii) light absorbed by chlorophyll-a (dashedline—Dev.1_(Chl-a));

FIG. 4 shows normalized absorption spectrum, normalized absorptionfactor versus wavelength (nm), for chlorophyll-b (dotted line—Chl-b) andspectral power distribution, spectral power (W/nm) versus wavelength(nm), for (i) a narrowband blue solid-state light source Dev.2 (solidline—Dev.2) and (ii) light absorbed by chlorophyll-b (dashedline—Dev.2_(Chl-b));

FIG. 5 shows normalized absorption spectrum, normalized absorptionfactor versus wavelength (nm), for chlorophyll-a (dotted line—Ch1-a) andspectral power distribution, spectral power (W/nm) versus wavelength(nm), for (i) a broadband blue solid-state light source Dev.3 (solidline—Dev.3) and (ii) light absorbed by chlorophyll-a (dashedline—Dev.3_(Chl-a));

FIG. 6 shows normalized absorption spectrum, normalized absorptionfactor versus wavelength (nm), for chlorophyll-b (dotted line—Chl-b) andspectral power distribution, spectral power (W/nm) versus wavelength(nm), for (i) a broadband blue solid-state light source Dev.4 (solidline—Dev.4) and (ii) light absorbed by chlorophyll-b (dashedline—Dev.4_(Chl-b));

FIG. 7 shows normalized absorption spectrum, normalized absorptionfactor versus wavelength (nm), for carotenoid (dotted line—Caro) andspectral power distribution, spectral power (W/nm) versus wavelength(nm), for (i) a broadband blue solid-state light source Dev.5 (solidline—Dev.5) and (ii) light absorbed by carotenoid (dashedline—Dev.5caro);

FIG. 8 shows spectral power distribution, spectral power versuswavelength (nm) for a white light emitting device (grow-light) Dev.6(solid line—Dev.6) utilizing a broadband blue solid-state light sourceand absorption spectrum, absorption (%) versus wavelength (nm), forchlorophyll-a pigment (dotted line—Chl-a);

FIG. 9 shows spectral power distribution, spectral power versuswavelength (nm) for Dev.6 (solid line—Dev.6) and McCree Curve (dashedline—McCree);

FIG. 10 shows normalized absorption spectra, normalized absorptionfactor versus wavelength (nm), for chlorophyll-a (dotted line—Chl-a) andchlorophyll-b (dashed line—Chl-b) and spectral power distribution,spectral power (W/nm) versus wavelength (nm), for a broadband fullspectrum blue solid-state light source Dev.7 (solid line—Dev.7);

FIG. 11 shows normalized absorption spectrum, normalized absorptionfactor versus wavelength (nm), for chlorophyll-a (dotted line—Chl-a) andspectral power distribution, intensity (W/nm) versus wavelength (nm),for light absorbed by chlorophyll-a (solid line—Dev.7_(Chl-a));

FIG. 12 shows normalized absorption spectrum, normalized absorptionfactor versus wavelength (nm), for chlorophyll-b (dashed line—Chl-b) andspectral power distribution, spectral power (W/nm) versus wavelength(nm), for light absorbed by chlorophyll-b (solid line—Dev.7_(Chl-b));

FIG. 13 shows absorption spectra, absorption (%) versus wavelength (nm),for photosynthetic pigments: (i) chlorophyll-a (dotted line—Chl-a), (ii)chlorophyll-b (dashed line—Chl-b), and spectral power distribution,spectral power versus wavelength (nm) for a purple light emitting device(grow-light) Dev.8 (solid line Dev.8) utilizing a broadband fullspectrum blue solid-state light source;

FIG. 14 shows spectral power distribution, spectral power versuswavelength (nm) for Dev.8 (dotted line—Dev.8) utilizing a broadband fullspectrum blue solid-state light source, and PAS (thick solid line—PAS);

FIG. 15 shows emission spectrum, normalized intensity versus wavelength(nm), for a white light emitting device (grow-light) Dev.9 (solid lineDev.9) utilizing a full spectrum white solid-state light source,Plankian locus (black body locus—BBL), normalized intensity versuswavelength (nm), for a CCT of 4000K (dashed line—4000K BBL), and McCreeCurve (dotted line—McCree);

FIG. 16 shows spectral power distribution, spectral power versuswavelength (nm) for purple grow-lights utilizing: (i) a narrowband bluesolid-state light source (dotted line—Narrowband Blue), (ii) a broadbandblue solid-state light source (dashed line—Broadband Blue), and (iii) abroadband full spectrum blue solid-state light source (thin solidline—Full Spectrum Blue) and PAS (thick solid line—PAS);

FIGS. 17A and 17B are schematic plan views of a grow-light according tothe invention comprising broadband blue solid-state light sources;

FIG. 18 shows radiant power spectrum, relative radiant power versuswavelength (nm), for a broadband blue solid-state light source Dev.10(solid line—Dev.10) and absorption spectra, absorption versus wavelength(nm) for chlorophyll-a (dotted line—Chl-a);

FIG. 19 shows radiant power spectrum, relative radiant power versuswavelength (nm), for a broadband blue solid-state light source Dev.11(solid line—Dev.11) and absorption spectra, absorption versus wavelength(nm) for chlorophyll-b (dotted line—Chl-b);

FIG. 20 shows radiant power spectrum, relative radiant power versuswavelength (nm), for a broadband red solid-state light source Dev.12(solid line—Dev.12);

FIG. 21 shows emission spectrum, normalized intensity versus wavelength(nm), for a grow-light Dev.13 (solid line—Dev.13) and absorptionspectra, normalized absorption versus wavelength (nm) for chlorophyll-a(dotted line—Chl-a);

FIG. 22 shows emission spectrum, normalized intensity versus wavelength(nm), for a grow-light Dev.14 (solid line—Dev.14); and

FIG. 23 shows emission spectrum, normalized intensity versus wavelength(nm), for a grow-light Dev.15 (solid line—Dev.15).

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention will now be described in detailwith reference to the drawings, which are provided as illustrativeexamples of the invention so as to enable those skilled in the art topractice the invention. Notably, the figures and examples below are notmeant to limit the scope of the present invention to a singleembodiment, but other embodiments are possible by way of interchange ofsome or all of the described or illustrated elements. Moreover, wherecertain elements of the present invention can be partially or fullyimplemented using known components, only those portions of such knowncomponents that are necessary for an understanding of the presentinvention will be described, and detailed descriptions of other portionsof such known components will be omitted so as not to obscure theinvention. In the present specification, an embodiment showing asingular component should not be considered limiting; rather, theinvention is intended to encompass other embodiments including aplurality of the same component, and vice-versa, unless explicitlystated otherwise herein. Moreover, applicants do not intend for any termin the specification or claims to be ascribed an uncommon or specialmeaning unless explicitly set forth as such. Further, the presentinvention encompasses present and future known equivalents to the knowncomponents referred to herein by way of illustration.

As described herein embodiments of the invention concern grow-lights(light emitting devices) comprising solid-state light sources (LEDs)that generate blue light with peak emission wavelengths correspondingwith the peak absorption wavelengths of chlorophyll and/or carotenoidpigments to promote photosynthesis and plant growth. The solid-statelight sources can be narrowband, broadband or full spectrum. In thispatent specification, narrowband blue light refers to light with a FWHMless than 25 nm, broadband blue light refers to light with a FWHM from30 nm to 80 nm, and full spectrum blue light refers to light with asubstantially constant intensity (i.e. an intensity variation of lessthan 25%) over a 40 nm wavelength range.

Purple light emitting grow-lights may comprise solid-state light sourcesof the invention used together with red light emitting LEDs or redphosphors that generate red light emissions with peak emissionwavelengths corresponding to the absorption peaks of Chlorophyllpigments in the red region of the spectrum. The light emitting devicemay further comprise a red LED or a red photoluminescence material thatgenerates far red light emission. This can increase photosynthesis whenused in combination with red light in the Photosynthetically ActiveRadiation (PAR), 400 nm to 700 nm, through the Emerson EnhancementEffect.

White light emitting grow-lights may further comprise broadband yellowto green emission photoluminescence materials (phosphors) for generatingwhite light. Such light can be beneficial in promoting plant growth andaiding visual inspection of plant growth.

In this specification Dev. # is used to denote both grow-lights (lightemitting devices) and solid-state light sources in accordance withembodiments of the invention.

FIG. 1A shows absorption spectra, absorption (%) versus wavelength (nm),for photosynthetic pigments: (i) chlorophyll-a (solid line—Chl-a), (ii)chlorophyll-b (dotted line—Chl-b), and (iii) carotenoid (dashedline—Caro).

As indicated in FIG. 1A, chlorophyll-a (Chl-a) has: (i) an absorptionpeak 10 a with a peak absorption of about 66% (0.66) at a peakabsorption wavelength of about 430 nm in the blue light region of thespectrum and (ii) a second absorption peak 10 b of about 58% (0.58) at apeak absorption wavelength of about 665 nm in the red light region ofthe spectrum. Chlorophyll-b (Chl-b) has: (i) an absorption peak 20 awith a peak absorption of about 85% (0.85) at a peak absorptionwavelength of about 465 nm in the blue light region of the spectrum and(ii) a second absorption peak 20 b of about 35% (0.35) at a peakabsorption wavelength of about 650 nm in the red light region of thespectrum. Carotenoid (Caro) has: an absorption peak 30 a with a peakabsorption of about 62% (0.62) at a peak absorption wavelength of about457 nm in the blue light region of the spectrum and (ii) a secondabsorption peak 30 b with a peak absorption wavelength of about 486 nmin the blue light region of the spectrum.

FIG. 1B is a Photosynthesis Action Spectrum (PAS), relativephotosynthetic response (%) versus wavelength (nm). The spectrum is anaverage spectrum for a plant including chlorophyll-a, chlorophyll-b andcarotenoid (β carotine) pigments. As is known, different plant speciesabsorb light differently and consequently have different PAS. The PASillustrated in FIG. 1B is an average of the PAS Curves of many differentplant species.

As indicated in FIG. 1B, the PAS has a maximum value (100%) peak 40 at awavelength around 440 nm in the blue light region of the spectrum and asecond, lower, peak 50 at a wavelength around 675 nm in the red lightregion of the spectrum. For wavelengths between the peaks 40, 50 in thegreen to yellow region of the spectrum (540 nm to 570 nm) there is adeep trough in the PAS which reaches a minimum value around 550 nm. Thetrough in the PAS suggests that light in the green to yellow region ofthe spectrum contributes only minimally to plant photosynthesis.

FIG. 1C shows a McCree Curve, average photosynthetic response toabsorbed photons at different wavelengths and is a plot of relativephotosynthetic response versus wavelength (nm). As with the PAS, theMcCree curve is a generalized (average) of the absorption curves ofmultiple different plants including chlorophyll-a, chlorophyll-b andcarotenoid (β carotine) pigments. As can be seen from FIG. 1C, thephotosynthetic quantum yield has a maximum value (100%) for wavelengthfrom about 600 nm to about 630 nm suggesting that, in contrast to thePAS (FIG. 1B) red light plays a greater role in photosynthesis rate thanblue light. Moreover, the McCree Curve indicates that green to yellowlight may also play a role in the photosynthesis process. The McCreecurve closely resembles the spectrum of daylight/sunlight forwavelengths from 380 nm to 730 nm.

Both the PAS and McCree Curve indicate that the plant growth efficiencyis not just photon intensity dependent but also wavelength dependent inthe blue to cyan region from 400 nm to 520 nm where plants have the mostabsorption efficiency. Embodiments of the inventions concern solid-statelight sources that generate light in the blue to cyan region whosespectral composition is configured to promote plant growth efficiency.

Photon Flux (PF), Photosynthetic Photon Flux (PPF), PhotosynthesisFactor, and Photosynthetic Photon Efficacy (PPE)

As is known, Photon Flux (PF) is a measure of the total number ofphotons (Photon count) emitted per second by a light source. Typically,photon flux is calculated using all photon wavelengths of light.

Photosynthetic Photon Flux (PPF) is a measure of the total amount ofphotosynthetically active radiation generated by a light source; that isthe photon flux (total number of photons emitted per second) by thesource over wavelengths of the Photosynthetically Active Radiation (PAR)from 400 nm to 700 nm. The calculation assumes that no photosynthesisoccurs at shorter or longer wavelengths. The photosynthetic photon fluxof a light source, PPFsource, is given by:

PPF _(source)=Σ₄₀₀ ⁷⁰⁰ P(λ)·dλ (μmol/s)

where P(λ) is the spectral power distribution (SPD) of the source.

Photon Flux (Photon count per second) is given by:

Photon Flux=PPF _(source) ×N _(A)×1000 (s ⁻¹)

where N_(A) is Avagadro's constant (6.02214076×10²³).

The photosynthetic photon flux of light absorbed by a pigment (pig.),PPF_(pig), is given by:

PPF _(pig.)=Σ₄₀₀ ⁷⁰⁰ P(λ)·B _(pig.)(λ)·dλ (μmol/s)

where B(λ) is the absorption spectrum of the pigment.

The photosynthesis factor, which gives a measure of the amount ofPhotosynthetic Photon Flux absorbed by a pigment is given by:

Photosynthesis Factor=PPF _(pig.) /PPF _(source) (%).

Photosynthesis Photon Efficacy (PPE or Kp) gives a measure of theefficacy of plant lighting. PPE is the photosynthetic photon flux (PPF)of the light source divided by input electric power to the light sourceand is given by:

PPE _(source) =PPF _(source)/electrical power (μmol/J).

Grow-Light Sources (Light Emitting Devices)

As described herein, embodiments of the invention can comprise agrow-light source (light emitting device) for horticultural lightingcomprising one or more blue solid-state light sources (LEDs) thatgenerate light with a peak emission wavelength λ_(pe) from 400 nm to 520nm (blue to cyan). The peak emission wavelengths can be selected tocorrespond to the peak absorption wavelengths of chlorophyll and/orcarotenoid pigments to promote photosynthesis and plant growth.

The one or more solid-state light sources may comprise one or moreInGaN/GaN LED chips that may generate narrowband blue light, broadbandblue light or full spectrum blue light. In embodiments, the one or moreLED chips may be packaged in a SMD (Surface Mount Device) package.

FIGS. 2A and 2B are schematic views of an SMD packaged light emittingdevice 100 in accordance with the invention in which FIG. 2A is a planview of the device and FIG. 2B is a sectional side view through A-A.

The light emitting device 100 is a packaged-type device comprising apackage 110, for example, an SMD (Surface Mounted Device) 2835 LEDpackage. The package 110 comprises a base 112 and side walls 114 thatextend upwardly from opposing edges of the base 112. The interiorsurfaces of the side walls 114 slope inwardly to their vertical axis ina direction towards the base 112 and, together with the interior surface(floor) of the base 112, define a cavity 116.

The cavity 116 contains one or more (2 as shown) InGaN-based LED dies(blue LED chips) 118 mounted on the floor (interior surface of the base)of the cavity 116. As indicated, the LED chips 118 can be electricallyconnected to the contact pads on the floor of the cavity by bond wires120. The contact pads are electrically connected to contact pads on thebase of the package 122 a, 122 b.

The cavity 116 is filled with a light transmissive (transparent)material (optical encapsulant) 124, such as silicone material. The lighttransmissive material 124 may contain light scattering particles orlight diffusive materials.

Grow-Lights Comprising Narrowband Blue Solid-State Light Sources

As described herein, embodiments of the invention can comprise agrow-light (light emitting device) for horticultural lighting comprisingone or more narrowband blue solid-state light sources that generatenarrowband light with a peak emission wavelength λ_(pe) from 400 nm to520 nm (blue to cyan) and a FWHM from 10 nm to 25 nm. The peak emissionwavelengths can be selected to correspond to the peak absorptionwavelengths of chlorophyll and/or carotenoid pigments to promotephotosynthesis and plant growth.

Solid-state light source, Dev.1, is a narrowband blue solid-state lightsource in accordance with the invention that is configured to promotephotosynthesis involving the chlorophyll-a pigment. Dev.1 comprises anarrowband InGaN/GaN LED that generates a narrowband emission with apeak emission wavelength (λ_(pe)=436 nm) corresponding to the peakabsorption wavelength of chlorophyll-a (about 430 nm) in the blue regionof the spectrum.

The optical characteristics of the narrowband blue solid-state lightsource Dev.1 are given in TABLE 1. As can be seen from the table, Dev.1has a peak emission wavelength λ_(pe) of about 430 nm and a FWHM ofabout 12 nm.

FIG. 3 shows spectral power distribution (SPD), spectral power (W/nm)versus wavelength (nm), for narrowband blue solid-state light sourceDev.1 (solid line—Dev.1) and the SPD of light absorbed by chlorophyll-a(dashed line—Dev.1_(Chl-a)). The SPD of light absorbed by chlorophyll-a(Dev.1_(Chl-a)) is derived by scaling spectral power values of the SPDof Dev.1 by the normalized absorption spectrum of Chl-a. The normalizedabsorption spectrum of Chl-a is the absorption spectrum of Chl-a thathas been normalized so that it has a maximum absorption value equal toone. As a result, the spectral power values absorbed by chlorophyll-ashould be multiplied by 0.66 to obtain absolute values. For visualcomparison, FIG. 3 also includes the normalized absorption spectrum,normalized absorption factor versus wavelength for the chlorophyll-apigment (dotted line—Chl-a).

The photosynthetic photon flux (PPF) generated by Dev.1, PPF_(Dev.1), is0.4166 μmol/s. The PPF absorbed by Chl-a pigment, PPF_(Chl-a), is 0.2342μmol/s giving a photosynthesis factor (PPF_(Chl-a)/PPF_(Dev.1)) of 56%.In TABLE 1, the values in parenthesis are calculated using thenormalized absorption spectrum. The photosynthetic photon efficacy (PPE)of Dev.1, PPE_(Dev.1), is 2.4353 μmol/J.

TABLE 1 Optical characteristics of solid-state light source Dev. 1 @ 25°C. and chlorophyll-a (Chl-a) λ_(pe) FWHM PPF_(Dev.1) PPF_(Chl-a)Photosynthesis PPE_(Dev.1) (nm) (nm) (μmol/s) (μmol/s) Factor (%)(μmol/J) 430 12 0.4166 0.2342 56 2.4353 (0.3549) (85)

Narrowband blue solid-state light source, Dev.2, is a narrowbandsolid-state light source in accordance with the invention that isconfigured to promote photosynthesis involving the chlorophyll-bpigment. Dev.2 comprises a narrowband InGaN LED that generates anarrowband emission with a peak emission wavelength (λ_(pe)=461 nm)corresponding to the peak absorption wavelength of chlorophyll-b (about465 nm) in the blue region of the spectrum.

The optical characteristics of the narrowband blue solid-state lightsource Dev.2 are given in TABLE 2. As can be seen from the table Dev.2has a peak emission wavelength λ_(pe) of about 468 nm and a FWHM ofabout 18 nm.

FIG. 4 shows spectral power distribution (SPD), spectral power (W/nm)versus wavelength (nm), for Dev.2 (solid line—Dev.2) and the SPD oflight absorbed by chlorophyll-b (dashed line—Dev.2_(Chl-b)). The SPD oflight absorbed by chlorophyll-b (Dev.2_(Chl-b)) is derived by scalingspectral power values of the SPD of Dev.2 by the normalized absorptionspectrum of Chl-b. The normalized absorption spectrum of Chl-b is theabsorption spectrum of Chl-b that has been normalized so that it has amaximum absorption value equal to one. As a result, the spectral powervalues absorbed by chlorophyll-b should be scaled by 0.85 to obtainabsolute values. For comparison, FIG. 4 also includes the normalizedabsorption spectrum, normalized absorption factor versus wavelength forthe chlorophyll-b pigment (dotted line—Chl-b).

The photosynthetic photon flux (PPF) generated by Dev.2, PPF_(Dev.2) is0.4147 μmol/s. The PPF absorbed by Chl-b, PPF_(Chl-b), is 0.28543 μmol/sgiving a photosynthesis factor (PPF_(Chl-b)/PPF_(Dev.2)) of 69%. InTABLE 2, the values in parenthesis are calculated using the normalizedabsorption spectrum. The photosynthetic photon efficacy (PPE) of Dev.2,PPE_(Dev.2), is 2.5108 μmol/J.

TABLE 2 Optical characteristics of solid-state light source Dev.2 @ 25°C. and chlorophyll-b (Ch1-b) λ_(pe) FWHM PPF_(Dev.2) PPF_(Chl-b)Photosynthesis PPE_(Dev.2) (nm) (nm) (μmol/s) (μmol/s) Factor (%)(μmol/J) 468 18 0.4147 0.28543 69 2.5108 (0.3358) (81)

Grow-Lights Comprising Broadband Blue Solid-State Light Sources

As described herein, embodiments of the invention can comprise agrow-light (light emitting device) for horticultural lighting comprisingone or more broadband solid-state light source that generates broadbandlight with a peak emission wavelength λ_(pe) from 400 nm to 520 nm (blueto cyan) and a FWHM of from 30 nm to 60 nm. The peak emissionwavelengths can be selected to correspond to the peak absorptionwavelengths of chlorophyll and/or carotenoid pigments to promotephotosynthesis and plant growth.

Broadband blue solid-state light source Dev.3 is a broadband solid-statelight source in accordance with the invention that is configured topromote photosynthesis involving the chlorophyll-a pigment. Dev.3comprises a broadband InGaN/GaN LED comprising multiple quantum wells(MQWs) that generate different wavelength narrowband blue emissions thatin combination generate a broadband emission with a peak emissionwavelength corresponding to the peak absorption wavelength ofchlorophyll-a (about 430 nm) in the blue region of the spectrum.

The optical characteristics of the broadband blue solid-state lightsource Dev.3 are given in TABLE 3. As can be seen from the table, Dev.3has a peak emission wavelength λ_(pe) of about 432 nm and a FWHM ofabout 38 nm.

FIG. 5 shows spectral power distribution (SPD), spectral power (W/nm)versus wavelength (nm), for Dev.3 (solid line—Dev.1) and the SPD oflight absorbed by chlorophyll-a (dashed line—Dev.3_(Chl-a)). The SPD oflight absorbed by chlorophyll-a (Dev.3_(Chl-a)) is derived by scalingspectral power values of the SPD of Dev.3 by the normalized absorptionspectrum of Chl-a. The normalized absorption spectrum of Chl-a is theabsorption spectrum of Chl-a that has been normalized so that it has amaximum absorption value equal to one. As a result, to obtain absolutespectral power values absorbed by chlorophyll-a, the spectral powervalue should be scaled by 0.66. For comparison, FIG. 5 also includes thenormalized absorption spectrum, normalized absorption factor versuswavelength for the chlorophyll-a pigment (dotted line—Chl-a).

The photosynthetic photon flux (PPF) generated by Dev.3, PPF_(Dev.3), is0.3464 μmol/s. The PPF absorbed by Chl-a, PPF_(Chl-a), is 0.1379 μmol/sgiving a photosynthesis factor (PPF_(Chl-a)/PPF_(Dev.3)) of 40%. InTABLE 3, the values in parenthesis are calculated using the normalizedabsorption spectrum. The photosynthetic photon efficacy (PPE) of Dev.3,PPE_(Dev.3), is 2.0149 μmol/J.

TABLE 3 Optical characteristics of solid-state light source Dev.3 @ 85°C. and chlorophyll-a (Chl-a) λ_(pe) FWHM PPF_(Dev.3) PPF_(Chl-a)Photosynthesis PPE_(Dev.3) (nm) (nm) (μmol/s) (μmol/s) Factor (%)(μmol/J) 433 38 0.3464 0.1379 40 2.0149 (0.2089) (60)

Broadband blue solid-state light source Dev.4 is a solid-state lightsource in accordance with the invention that is configured to promotephotosynthesis involving the chlorophyll-b pigment. Dev.4 comprises abroadband InGaN/GaN LED comprising multiple quantum wells (QWs) thatgenerate different wavelength narrowband components that in combinationgenerate a broadband emission with a peak emission wavelengthcorresponding to the peak absorption wavelength of chlorophyll-b (about465 nm) in the blue region of the spectrum.

The optical characteristics of the broadband blue solid-state lightsource Dev.4 are given in TABLE 4. As can be seen from the table, Dev.4has a peak emission wavelength λ_(pe) of about 462 nm and a FWHM ofabout 41 nm.

FIG. 6 shows spectral power distribution (SPD), spectral power (W/nm)versus wavelength (nm), for Dev.4 (solid line—Dev.4) and the SPD oflight absorbed by chlorophyll-b (dashed line—Dev.4_(Chl-b)). The SPD oflight absorbed by chlorophyll-b (Dev.4_(Chl-b)) is derived by scalingspectral power values of the SPD of Dev.1 by the normalized absorptionspectrum of Chl-b. The normalized absorption spectrum of Chl-b is theabsorption spectrum of Chl-b that has been normalized so that it has amaximum absorption value equal to one. As a result, to obtain absolutespectral power values absorbed by chlorophyll-b, the spectral powervalue should be scaled by 0.85. For comparison, FIG. 6 also includes thenormalized absorption spectrum, normalized absorption versus wavelengthfor the chlorophyll-b pigment (dotted line—Chl-b).

The photosynthetic photon flux (PPF) generated by Dev.4, PPFDev.4, is0.3503 μmol/s. The PPF absorbed by Chl-b, PPF_(Chl-b), is 0.2025 μmol/sgiving a photosynthesis factor (PPF_(Chl-b)/PPF_(Dev.4)) of 58%. InTABLE 4, the values in parenthesis are calculated using the normalizedabsorption spectrum. The photosynthetic photon efficacy (PPE) of Dev.4,PPE_(Dev.4), is 2.0995 μmol/J.

TABLE 4 Optical characteristics of solid-state light source Dev.4 @ 85°C. and chlorophyll-b (Chl-b) λ_(pe) FWHM PPF_(Dev.4) PPF_(Chl-b)Photosynthesis PPE_(Dev.4) (nm) (nm) (μmol/s) (μmol/s) Factor (%)(μmol/J) 462 41 0.3503 0.2025 58 2.0995 (0.2382) (68)

Broadband blue solid-state light source Dev.5 is a solid-state lightsource in accordance with the invention that is configured to promotephotosynthesis involving the carotenoid pigment. Dev.5 comprises anbroadband InGaN/GaN LED comprising multiple quantum wells (QWs) thatgenerate different wavelength narrowband components that in combinationgenerate broadband emission peaks with peak emission wavelengthcorresponding to the peak absorption wavelengths (about 457 nm and about487 nm) of carotenoid.

The measured optical characteristics of the broadband solid-state lightsource Dev.5 are given in TABLE 5. As can be seen from the table, Dev.5has a maximum emission peak at a peak emission wavelength λ_(pe) ofabout 495 nm and a FWHM of about 56 nm.

FIG. 7 shows spectral power distribution (SPD), spectral power (W/nm)versus wavelength (nm), for Dev.5 (solid line—Dev.5) and the SPD oflight absorbed by carotenoid (dashed line—Dev.5_(Caro)). The SPD oflight absorbed by carotenoid (Dev.5_(Caro)) is derived by scalingspectral power values of the SPD of Dev.5 by the normalized absorptionspectrum of Caro. The normalized absorption spectrum of Caro is theabsorption spectrum of Caro that has been normalized so that it has amaximum absorption value equal to one. As a result, to obtain absolutespectral power values absorbed by carotenoid, the spectral power valueshould be scaled by 0.62. For comparison, FIG. 7 also includes theabsorption spectrum, absorption versus wavelength for the carotenoidpigment (dotted line—Caro). As can be seen from FIG. 7 , Dev.6 generatesa second broadband peak at 467 nm with a FWHM of about 25 nm.

The photosynthetic photon flux (PPF) generated by Dev.5, PPF_(Dev.5), is0.2221 μmol/s. The PPF absorbed by Caro, PPF_(Caro), is 0.1027 μmol/sgiving a photosynthesis factor (PPF_(Caro)/PPF_(Dev.5)) of 47%. In TABLE5, the values in parenthesis are calculated using the normalizedabsorption spectrum. The photosynthetic photon efficacy (PPE) of Dev.5,PPE_(Dev.5), is 1.4246 μmol/J.

TABLE 5 Optical characteristics of solid-state light source Dev.5 @ 85°C. and carotenoid (Caro) λ_(pe) FWHM PPF_(Dev.5) PPF_(Caro)Photosynthesis PPE_(Dev.5) (nm) (nm) (μmol/s) (μmol/s) Factor (%)(μmol/J) 495 56 0.2221 0.1027 47 1.4246 (0.1657) (75)

In other embodiments, the solid-state light source for carotenoid maycomprise two broadband LEDs for generating light with a peak emissionwavelength corresponding to a respective one of the carotenoidabsorption peak wavelengths.

White Grow-Light: Broadband Blue Solid-State Light Source

Dev.6 is a white light emitting device (grow-light) in accordance withthe invention that utilizes a broadband blue solid-state light sourceand is configured to promote photosynthesis involving the chlorophyll-apigment. The broadband solid-state light source comprises a broadbandInGaN/GaN LED comprising multiple quantum wells (MQWs) that generatedifferent wavelength narrowband components that in combination generatea broadband emission with a peak emission wavelength corresponding tothe peak absorption wavelength of chlorophyll-a (about 430 nm) in theblue region of the spectrum.

The white light emitting device Dev.6 may comprise a packaged devicesuch as that illustrated in FIGS. 2 a and 2B and comprise a 2835 SMDpackage containing a single broadband blue LED, a red photoluminescencematerial that generates light with a peak emission wavelength in orangeto red (from about 640 nm to about 675 nm) region of the spectrumcorresponding to the red absorption peak of chlorophyll-a, and a greento yellow photoluminescence material that generates light with a peakemission wavelength in the green to yellow (from about 540 nm to about600 nm) region of the spectrum. More particularly, Dev.6 comprises aCalcium Aluminum Silicon Nitride phosphor (CASN) of general formulaCaAlSiN₃:Eu²⁺ with a peak emission wavelength of about 615 nm and a YAGbased phosphor with a peak emission wavelength of about 540 nm to 560nm. In operation, the light emitting device Dev.6 generates white lightcomprising a combination of blue light generated by the solid-statelight source and yellow and red photoluminescence light generated by thephosphor materials.

FIG. 8 shows spectral power distribution, spectral power versuswavelength (nm) for the white light emitting device (grow-light) Dev.6(solid line—Dev.6) and the absorption spectrum, absorption (%) versuswavelength (nm), for chlorophyll-a pigment (dotted line—Chl-a). FIG. 9shows spectral power distribution, spectral power versus wavelength (nm)for Dev.6 (solid line—Dev.6) and the McCree curve (dashed line—cCree).As can be seen from FIG. 9 , white light generated by Dev.6 has aspectral composition whose shape substantially matches that of theMcCree Curve. Such a correspondence in spectral composition promotesphotosynthesis as well as increase PPF efficacy of the device.

Grow-Lights Comprising Broadband Full Spectrum Blue Solid-State LightSource

As described herein embodiments of the invention can comprise a lightemitting device (grow-light) for horticultural lighting comprising afull spectrum blue solid-state light source that generates full spectrumblue light that generate light whose spectral composition more closelymatches (resembles) sunlight/daylight at wavelengths in the blue to cyanregion of the spectrum, more specifically for wavelengths from 400 nm to520 nm of the Photosynthetically Active Radiation (PAR). Morespecifically, broadband full spectrum blue light has a flat emissionmaxima whose intensity is substantially constant (varies less than about10%) over a wavelength range of at least 40 nm. Full Spectrum Bluesolid-state light sources may comprise multiple broadband solid-statelight sources.

Full spectrum blue solid-state light source Dev.7 is a full spectrumblue light source in accordance with the invention that is configured topromote photosynthesis involving both chlorophyll-a (Chl-a) andchlorophyll-b (Chl-b). Dev.7 comprises a combination of two InGaN/GaNMQW broadband blue LEDs. The first broadband LED generates blue lightwith a peak emission wavelength of 432 nm. The second broadband LEDgenerates blue light with a peak emission wavelength of 451 nm. The peakemission wavelengths of the broadband blue LEDs are selected such thatDev.7 has a peak emission wavelength lying between the peak absorptionwavelengths of chlorophyll-a and chlorophyll-b (430 nm and 465 nm).

A particular advantage of using a single broadband MQW LED chip togenerate broadband blue light, as compared to using multiple narrowbandBlue LED chips, is a substantial reduction in the numbers of LEDsrequired to generate the broad blue emission. This is particularlyimportant in horticultural applications where the most popular SMD(Surface Mount Device) package 2835 or 3030 which have about a 6 mmsquare light emitting area and can accommodate one to three LED chips,for example three middle power chips or one high power chip. The maximumFWHM that can be achieved by three narrowband blue chips are about 45nm. While large form factor packages such as COB (Chip On Board) canachieve greater FWHM using three or more chips, such packaged devicesare not compatible with linear area lighting required in horticultureapplications. Furthermore, multiple die bonding in packaging manufacturewill increase cost and reduce production rate.

The optical characteristics of the broadband full spectrum bluesolid-state light source Dev.6 are given in TABLE 6. As can be seen fromthe table, Dev.7 has a maximum emission peak at a peak emissionwavelength λ_(pe) of about 448 nm and a FWHM of about 64 nm. FIG. 10shows spectral power distribution (SPD), spectral power (W/nm) versuswavelength (nm), for Dev.7 (solid line—Dev.7) and normalized absorptionspectra, normalized absorption factor versus wavelength (nm), forchlorophyll-a (dotted line—Chl-a) and chlorophyll-b (dashed line—Chl-b).As can be seen from FIG. 10 , the spectral power distribution of lightgenerated by Dev.7 comprises a broadband emission with a flattened(clipped) emission maxima 60 whose spectral power is substantiallyconstant (varies less than about 10%) for wavelength from about 430 nmto about 470 nm.

FIG. 11 shows spectral power distribution (SPD), spectral power (W/nm)versus wavelength (nm), of light absorbed by chlorophyll-a (solidline—Dev.7_(Chl-a)). The SPD of light absorbed by chlorophyll-a(Dev.6_(Chl-a)) is derived by scaling spectral power values of the SPDof Dev.7 by the normalized absorption spectrum of Chl-a. The normalizedabsorption spectrum of Chl-a is the absorption spectrum of Chl-a thathas been normalized so that it has a maximum absorption value equal toone. As a result, to obtain absolute spectral power values absorbed bychlorophyll-a, the spectral power value should be scaled by 0.66. Forcomparison, FIG. 11 also includes the normalized absorption spectrum,normalized absorption factor versus wavelength, for the chlorophyll-apigment (dotted line—Chl-a).

FIG. 12 shows spectral power distribution (SPD), spectral power (W/nm)versus wavelength (nm), of light absorbed by chlorophyll-b (solidline—Dev.7_(Chl-b)). The SPD of light absorbed by chlorophyll-b(Dev.7_(Chl-b)) is derived by scaling spectral power values of the SPDof Dev.6 by the normalized absorption spectrum of Chl-b. The normalizedabsorption spectrum of Chl-b is the absorption spectrum of Chl-b thathas been normalized so that it has a maximum absorption value is equalto one. As a result to obtain absolute spectral power values absorbed bychlorophyll-b, the spectral power value should be scaled by 0.85. Forcomparison, FIG. 12 also includes the absorption spectrum, absorptionfactor versus wavelength for the chlorophyll-b pigment (dashedline—Chl-b).

The photosynthetic photon flux (PPF) generated by Dev.7, PPF_(Dev.)7, is0.6370 μmol/s and the photosynthetic photon efficacy (PPE) is 1.9076μmol/J. The PPF absorbed by Chl-a, PPF_(Chl-a), is 0.1790 μmol/s givinga photosynthesis factor (PPF_(Chl-a)/PPF_(Dev.7)) for Chl-a of 28%. ThePPF absorbed by Chl-b, PPF_(Chl-b), is 0.3391 μmol/s giving aphotosynthesis factor (PPF_(Chl-b)/PPF_(Dev.7)) for Chl-b of 53%. ThePPF absorbed by Caro, PPF_(Caro), is 0.2917 μmol/s giving aphotosynthesis factor (PPF_(Caro)/PPF_(Dev.7)) for Caro of 46%. In TABLE6, the values in parenthesis are calculated using the normalizedabsorption spectrum.

TABLE 6 Optical characteristics of solid-state light source Dev. 7 @ 85°C. λ_(pe) FWHM PPF (μmol/s) Photosynthesis factor (%) PPE_(Dev. 7) (nm)(nm) PPF_(Dev. 7) PPF_(Chl-a) PPF_(Chl-b) PPF_(Caro) Chl-a Chl-b Caro(μmol/J) 448 64 0.6370 0.1790 0.3391 0.2917 28 53 46 1.9076 (0.2712)(0.3989) (0.4705) (43) (63) (74)

Purple Grow-Light: Broadband Full Spectrum Blue Solid-State Light Source

Dev.8 is a purple light emitting device (grow-light) in accordance withthe invention that utilizes a broadband full spectrum blue solid-statelight source and is configured to promote photosynthesis involving thechlorophyll-a and chlorophyll-b pigments. The full spectrum solid-statelight source comprises a combination of two InGaN/GaN MQW broadband blueLEDs. The first broadband LED generates blue light with a peak emissionwavelength of 432 nm. The second broadband LED generates blue light witha peak emission wavelength of 451 nm. The peak emission wavelengths ofthe broadband blue LEDs are selected such that Dev.8 has a peak emissionwavelength lying between the peak absorption wavelengths ofchlorophyll-a and chlorophyll-b (430 nm and 465 nm).

The purple light emitting device Dev.8 comprises a 2835 SMD packagecontaining the two broadband blue LEDs and a red photoluminescencematerial that generates light with a peak emission wavelength in theorange to red (from about 640 nm to about 675 nm) region of the spectrumcorresponding to the red absorption peaks of chlorophyll-a andchlorophyll-b. More particularly, Dev.8 comprises a Calcium AluminumSilicon Nitride phosphor (CASN) of general formula CaAlSiN₃:Eu²⁺ with apeak emission wavelength of 660 nm. The light emitting device Dev.8generates purple light comprising a combination of blue light generatedby the solid-state light source and red photoluminescence lightgenerated by the red phosphor.

FIG. 13 shows absorption spectra, absorption (%) versus wavelength (nm),for photosynthetic pigments: (i) chlorophyll-a (dotted line—Chl-a), (ii)chlorophyll-b (dashed line—Chl-b), and spectral power distribution,spectral power versus wavelength (nm) for the purple grow-light (lightemitting device) Dev.8 (solid line Dev.8).

FIG. 14 shows spectral power distribution, spectral power versuswavelength (nm) for Dev.8 (thin solid line—Dev.8) and PAS (thick solidline—PAS). As can be seen from FIG. 14 light generated by Dev.8 has aspectral composition whose shape substantially matches that of the PAS.Such a correspondence in spectral composition promotes photosynthesis aswell as increase PPF efficacy of the device.

White Grow-Light: Broadband Full Spectrum Blue Solid-State Light Source

Dev.9 is a white light emitting device (grow-light) in accordance withthe invention that utilizes a broadband full spectrum blue solid-statelight source and is configured to promote photosynthesis involving thechlorophyll and carotenoid pigments. The full spectrum solid-state lightsource comprises a combination of two InGaN/GaN MQW broadband LEDs. Thefirst broadband LED generates blue light with a peak emission wavelengthof 432 nm. The second broadband LED generates blue light with a peakemission wavelength of 451 nm.

The white light emitting device Dev.9 comprises a 2835 SMD packagecontaining the two broadband blue LEDs, a red photoluminescence materialthat generates light with a peak emission wavelength in orange to red(from about 640 nm to about 675 nm) region of the spectrum correspondingto the red absorption peak of chlorophyll-a, and a green to yellowphotoluminescence material that generates light with a peak emissionwavelength in the green to yellow (from about 540 nm to about 600 nm)region of the spectrum. More particularly, Dev.9 comprises a CalciumAluminum Silicon Nitride phosphor (CASN) of general formulaCaAlSiN₃:Eu²⁺ with a peak emission wavelength of 650 nm and a YAG basedphosphor with a peak emission wavelength of 510 nm to 570 nm. The lightemitting device Dev.9 generates white light with a CCT of about 4000Kthat comprises a combination of broadband full spectrum blue lightgenerated by the solid-state light source and green to redphotoluminescence light generated by the photoluminescence materials. Acombination of a Broadband blue with FWHM greater than about 30 nm witha cyan emitting phosphor with a peak emission wavelength from 510 nm to530 nm are important for generating light that mimics (closelyresembles) sunlight.

FIG. 15 shows emission spectrum, normalized intensity versus wavelength(nm), for a white light emitting device (grow-light) Dev.9 (solid lineDev.9) utilizing a broadband full spectrum blue solid-state lightsource, Planckian locus (black body locus—BBL), normalized intensityversus wavelength (nm), for a CCT of 4000K (dashed line—4000K BBL), andMcCree curve (dotted line—McCree). As can be seen from FIG. 15 , whitelight generated by Dev.9 has a spectral composition that substantiallymatches the Planckian locus of a black body radiator of 4000K forwavelength from about 420 nm to about 650 nm indicating that the lightclosely resembles that of daylight (4000K). Moreover, it can be seenthat white light generated by Dev.9 has a spectral composition whoseshape closely matches that of the McCree Curve. Such a correspondence inspectral composition with the McCree Curve indicates that Dev.9 mayincrease plant photosynthesis active yield.

In various embodiments of the present invention, in particular thoseutilizing broadband and broadband full spectrum blue solid state lightsources, a grow-light (light emitting device) advantageously generateslight who spectral composition matches (resembles) the PAS or McCreeCurve in the blue region of the spectrum.

As shown in FIGS. 14 and 16 when such a broadband full spectrum blueemission is used with a red phosphor emitting with a peak emissionwavelength of about 660 nm, purple light generated by the grow-lightclosely matches the PAS. For comparison, FIG. 16 also includes showsspectral power distribution, spectral power versus wavelength (nm) forpurple grow-lights utilizing: (i) a narrowband blue solid-state lightsource (dotted line—Narrowband Blue) and (ii) a broadband bluesolid-state light source (dashed line—Broadband Blue). It is to be notedthat each light source generates blue light with the same photon energy(area under the curve). As can be seen from FIG. 16 , grow-lightsutilizing both narrowband and broadband blue solid-state light sourceshave an emission spectrum with a peak that far exceeds the PAS. This isa result of their photon energy being distributed over a shorter rangeof wavelengths compared with broadband full spectrum source. As a resultof the very broad emission spectrum of the broadband full spectrum, inwhich the photo energy is spread over a greater wavelength range, thisleads to an increase in photosynthesis.

As shown in FIG. 16 , when such a broadband full spectrum blue emissionis used with broadband white conversion phosphor materials (cyan to red)emitting from about 500 nm to 660 nm white light generated by thegrow-light substantially matches the McCree Curve.

Grow-Lights Comprising Broadband Blue Light Emitting Devices

In accordance with aspects of the invention, there are provided purplegrow-lights, for example linear grow-lights, which can comprise acombination of one or more broadband blue light emitting devicesaccording to the invention and one or more broadband red light emittingdevices. In embodiments, the broadband blue light emitting devices andbroadband red light emitting devices comprise package devices.

FIGS. 17A and 17B are schematic views of grow-lights 200, for example T8linear lamps, according to the invention. Each grow-light 200 maycomprise a linear (elongate strip) substrate 210, for example a metalcore printed circuit board (MCPCB), having a plurality of packagedbroadband light emitting devices 220 mounted along its length. Asillustrated the light emitting devices 220 can be arranged as a lineararray extending in the direction of elongation of the substrate.

The light emitting devices 220 may comprise: (i) a broadband blue lightemitting device (Blue Chl-a LED) 220 a with a peak emission wavelength(e.g. about 420 nm to 450 nm) substantially matching the chlorophyll-a(Chl-a) absorption peak, (ii) a broadband blue light emitting device(Blue Chl-b LED) 220 b with a peak emission wavelength (e.g. about 460nm to 470 nm) substantially matching the chlorophyll-b (Chl-b)absorption peak, or (iii) a broadband red light emitting device (Red ChlLED) 220 r with a peak emission wavelength (e.g. about 640 nm to about675 nm) substantially matching the chlorophyll-a (Chl-a) andchlorophyll-b (Chl-b) absorption peaks in the red region of thespectrum.

The Blue Chl-a LED 220 a and Blue Chl-b LED 220 b may comprise, forexample, the packaged light emitting device 100 of FIGS. 2A and 2Bcomprising two MQW broadband LED chips 118. The peak emissionwavelengths of the MQW broadband LED chips 118 can be the same or may bedifferent.

The Red LED 220 r may comprise, for example, a packaged PhosphorConverted Red LED (PC Red LED) that is based on packaged light emittingdevice 100 of FIGS. 2A and 2B. For a red light emitting device 220 r,the packaged light emitting device 100 typically comprises twonarrowband blue LED chips 118 and the cavity 116 of the package 112 isfilled with a light transmissive medium 122 that incorporates a redphotoluminescence material. The red photoluminescence material generateslight with a peak emission wavelength in the orange to red (from about640 nm to about 675 nm) region of the spectrum corresponding to the redabsorption peaks of chlorophyll-a and chlorophyll-b (i.e. 10 b and 20 bof FIG. 1A). In embodiments, the red photoluminescence material maycomprise a Calcium Aluminum Silicon Nitride phosphor (CASN) of generalformula CaAlSiN₃:Eu²⁺ with a peak emission wavelength of about 660 nm.

The Photosynthetic Photon Flux (PPF) for the Blue Chl-a LEDs, Blue Chl-bLEDs, and Red Chl LEDs may be substantially the same, that is eachsource generates substantially the same the total number of photons(photon count) per second (photon flux).

The inventors have determined that grow-lamps can be provided that areoptimized to a given for application by appropriate selection of theratio of Blue Chl LEDs (Chl-a+Chl-b) to Red Chl LEDs, more specificallythe ratio of Blue photon count (i.e. Blue photon flux PF_(Blue) forwavelengths in the blue region of the spectrum) to Red photon count(i.e. Red photon flux for wavelengths in the red region of thespectrum). Moreover, grow-lamps can be optimized to a given forapplication by appropriate selection of the ratio of Blue Chl-a LEDs toBlue Chl-b LEDs, more specifically the ratio of Blue Chl-a photon count(i.e. Blue photon flux for wavelengths in the blue region of thespectrum corresponding to the Chl-a blue absorption peak) to Blue Chl-bphoton count (i.e. Blue photon flux for wavelengths in the blue regionof the spectrum corresponding to the Chl-b blue absorption peak). Inthis way, grow-lamps can be provided that are optimized to a given forapplication such as promoting photosynthesis or sole-source lighting forpromoting photosynthesis or for promoting plant propagation or promotingflowering.

The grow-lamp 200 of FIG. 17A comprises a plurality of Blue Chl-a LEDs220 a and Red Chl LEDs 220 r. As illustrated, the ratio of the number ofBlue Chl-a LEDs 220 a to the number of Red Chl LEDs 220 r is 1:1. In thecase where there are equal numbers of Blue Chl-a and RED Chl LEDs andeach LED emits substantially the same total number of photons per second(i.e. they have substantially the same photon flux), the spectralcomposition of light generated by the grow-light will have a ratio ofblue photon count (Blue photon flux PF_(Blue)) to red photon count (Redphoton flux PF_(Red)) which is about 1:1 (1.0±0.3:1.0, i.e. ratios from0.7:1 to 1.3:1). The inventors have determined that a grow-light havinga spectrum comprising substantially an equal photon count (photon flux)of Blue Chl-a and Red Chl photons can promote photosynthesis. It will beappreciated that in other arrangements different ratios of Blue Chl-aphotons to RED Chl photons may be used.

Referring to FIG. 17B, the grow-lamp 200 comprises a plurality of BlueChl-a LEDs 220 a, Blue Chl-b LEDs 220 b, and Red Chl LEDs 220 r. Asillustrated, the ratio of the combined number of Blue Chl-a LEDs andChl-b LEDs 220 a, 220 b to the number of Red Chl LEDs 220 r is 1:1. Inthe case each LED emits substantially the same total number of photonsper second (i.e. they have substantially the same photon flux), thespectral composition of light generated by the grow-light will have aratio of blue photon count (Blue photon flux PF_(Blue)) to red photoncount (Red photon flux PF_(Red)) which is about 1:1 (1.0±0.3:1.0, i.e.ratios from 0.7:1 to 1.3:1). The inventors have determined that agrow-light having a spectrum comprising a substantially equal photoncount (Blue photon flux PFB_(Blue)) of Blue Chl-a+Blue Chl-b photons(Blue photon flux PF_(Blue)) and Red Chl photons (Red photon fluxPF_(Red)) can promote photosynthesis.

In other arrangements the Blue photon count (Blue photon flux PF_(Blue))can be greater than the Red photon count (Red photon flux PF_(Red)), forexample a ratio of about 3:1 (3.0±0.5:1.0, i.e. ratios from 2.5:1 to3.5:1). The inventors have determined that a grow-light having aspectrum comprising a greater blue photon count (Blue photon fluxPF_(Blue)) of Blue Chl-a+Blue Chl-b photons (Blue photon flux PF_(Blue))than Red photon count (Red photon flux PF_(Red)) can promotepropagation.

In yet further arrangements, the Red photon count (Red photon fluxPF_(Red)) can be greater than Blue photon count (Blue photon fluxPF_(Blue)), for example a ratio of about 3:1 (3.0±0.5:1.0, i.e. ratiosfrom 2.5:1 to 3.5:1). The inventors have determined that a grow-lighthaving a spectrum comprising a greater red photon count (Red photon fluxPF_(Red)) than Blue photon count (Red photon flux PF_(Red)) can promoteflowering.

Moreover, in arrangements that utilize both Blue Chl-a LEDs and BlueChl-b LEDs, the Blue Chl-a photon count (Blue photon fluxPF_(Blue-Chl-a)) can be greater than the Blue Chl-b photon count (Bluephoton flux PF_(Blue-Chl-b)), for example a ratio of about 3:1(3.0±1.0:1.0, i.e. ratios from 2:1 to 4:1), that is about 75% of theblue light is generated by the Blue Chl-a LEDs.

Photon flux ratios for different grow-light application are tabulated inTABLE 7.

TABLE 7 Photon count (flux) ratios for different applications Grow-lightapplication PF_(Blue):PF_(Red) PF_(Blue-Chla):PF_(Blue-Chlb)Photosynthesis 1:1 (1.0 ± 0.3:1.0) 1:0 Photosynthesis 1:1 (1.0 ±0.3:1.0) 3:1 (3.0 ± 1.0:1.0) (sole-source lighting) Propagation 3:1 (3.0± 0.5:1.0) 3:1 (3.0 ± 1.0:1.0) Flowering 1:3 (1.0:3.0 ± 0.5) 3:1 (3.0 ±1.0:1.0)

Dev.10 is a solid-state blue light source (Blue Chl-a LED) comprising aSMD 2835 packaged broadband blue light emitting device in accordancewith the invention that comprises two broadband MQW LEDs with a peakemission wavelength corresponding to the chlorophyll-a (Chl-a)absorption peak.

Dev.11 is a solid-state blue light source (Blue Chl-b LED) comprising aSMD 2835 packaged broadband blue light emitting device in accordancewith the invention that comprises two broadband MQW LEDs with a peakemission wavelength corresponding to the chlorophyll-b (Chl-b)absorption peak.

Dev.12 is a solid-state red light source (Red Chl LED) comprising a SMD2835 packaged PC Red LED (Red Chl LED) with a peak emission wavelength(about 660 nm) corresponding to the chlorophyll-a (Chl-a) andchlorophyll-b (Chl-b) absorption peaks in the red region of thespectrum.

Each of devices Dev.10 to Dev.12 are 0.2 W devices with a 3V forwarddrive voltage.

TABLE 8 tabulates the measured optical characteristics of packaged lightemitting devices Dev.10 to Dev.12. FIG. 18 shows radiant power spectrum,relative radiant power versus wavelength (nm), for the broadband bluesolid-state light source (Blue Chl-a LED) Dev.10 (solid line—Dev.10) andabsorption spectra, absorption versus wavelength (nm) for chlorophyll-a(dotted line—Chl-a). FIG. 19 shows radiant power spectrum, relativeradiant power versus wavelength (nm), for the broadband blue solid-statelight source (Blue Chl-a LED) Dev.11 (solid line—Dev.11) and absorptionspectra, absorption versus wavelength (nm) for chlorophyll-b (dottedline—Chl-b). FIG. 20 shows radiant power spectrum, relative radiantpower versus wavelength (nm), for a broadband red solid-state lightsource (Red Chl LED) Dev.12 (solid line—Dev.12).

As can be seen from TABLE 8, each of devices Dev.10 to Dev.12 havesubstantially the same PPF and PPE. Referring to FIG. 18 , it is to benoted that Dev.10 (Blue Chl-a LED) has an emission spectrum thatsubstantially matches that of Chl-a with a first peak emissionwavelength λ_(pe) of about 426 nm and second peak emission wavelengthλ_(pe) of about 437 nm and a FWHM of about 27 nm. Referring to FIG. 19 ,it is to be noted that Dev.11 (Blue Chl-b LED) has an emission spectrumthat substantially matches that of Chl-b with a peak emission wavelengthλ_(pe) of about 462 nm and a FWHM of about 34 nm.

Referring to FIG. 20 , it is to be noted that Dev.12 (Red Chl LED) hasan emission spectrum with a red peak emission wavelength λ_(pe) of about660 nm and a FWHM of about 82 nm. It should also be noted that there isa lower intensity peak 240 in the blue region of the spectrum with apeak emission wavelength λ_(pe) of about 450 nm. The blue peak 240corresponds to unconverted narrowband blue excitation light. A benefitof not converting all of the excitation light is that can optimize theQuantum Efficiency (QE) and PPE of the device.

TABLE 8 Measured optical characteristics of solid-state light sourceDev. 10 (Blue Chl-a), Dev. 11 (Blue Chl-b), and Dev. 12 (Red Chl) @ 85°C. λ_(pe1) λ_(pe2) FWHM PPF PPE Device (nm) (nm) (nm) (μmol/s) (μmol/J)Dev.10¹ 425 437 27 0.41 2.21 Dev.11¹ 462 — 34 0.43 2.52 Dev.12² 660 — 820.42 2.41 ¹PPF and PPE includes wavelengths 400 nm to 700 nm ²PPF andPPE includes wavelengths 400 nm to 780 nm

Solid-state grow-lights, Devs.13 to 15, each comprise a T8 solid-stategrow-light comprising a total of one hundred and eight broadband lightsources (Blue Chl-a—Dev.10, Blue Chl-b—Dev.11, Red Chl—Dev.12). Dev.13is configured to promote photosynthesis, Dev.14 is configured to promotephotosynthesis by sole-source lighting, and Dev.15 is configured topromote flowering.

The composition of solid-state grow-lights, Devs. 13 to 15 are given inTABLE 9. As can be seen from TABLE 9, Dev.13 comprises fifty fourbroadband Blue Chl-a LEDs and fifty four broadband Red Chl LEDs.Assuming that the Blue Chl-a LEDs and Red Chl LEDs each emitsubstantially the same number of photons per second, then the photoncount of Blue chl-a to Red is 1:1.

As can be seen from TABLE 9, Dev.14 comprises forty eight broadband BlueChl-a LEDs, eight broadband Blue Chl-b LEDs and fifty two broadband RedChl LEDs. In this arrangement, the ratio of blue photon count(Chl-a+Chl-b) to red photon count is 1:1. In terms of the composition ofblue light, the ratio of Blue Chl-a to Blue Chl-b photon count is about6:1 (48:8).

As can be seen from TABLE 9, Dev.15 comprises seventeen broadband BlueChl-a LEDs, two broadband Blue Chl-b LEDs and eighty nine broadband RedChl LEDs. In this arrangement, the ratio of blue photon count(Chl-a+Chl-b) to red photon count is about 1:4 (13:55), that is thespectral composition of light generated by Dev.15, has in terms ofphoton count, a predominance of red light. In terms of the compositionof blue light, the ratio of Blue Chl-a to Blue Chl-b photon count isabout 8:1 (17:2).

TABLE 9 Composition of solid-state grow-lights Dev. 13 to Dev. 16 No. ofbroadband light sources Ratio of light sources Grow-light Blue Chl-aBlue Chl-b Red Ch1 Chl-a:Chl-b:Red (application) (Dev. 10) (Dev. 11)(Dev. 13) Total Chl-a:Chl-b:Red Blue:Red Dev. 13 54 — 54 108 1:0:1 1:1(Photosynthesis) Dev. 14 48 8 52 108 11:2:13 1:1 (sole-source) Dev. 1517 2 89 108 11:2:55 1:3 (Flowering) Note: Each broadband light sourcehas substantially the same photon count

TABLE 10A and 10B tabulates measured optical characteristics ofgrow-lights Dev.13 to Dev.15. In TABLE 10A: PPF_(x-y) is thePhotosynthetic photon flux for wavelengths from x−y nm; PPE_(x-y) isPhoton flux Efficacy for wavelengths from x-y nm; and PF_(x-y) is thePhoton flux (photon count per second) for wavelengths from x-y nm. InTABLE 10B: PPF_(Blue) is the Photosynthetic photon flux for bluewavelengths from 400-500 nm; PF_(Blue) is the Photon flux (photon countper second) for blue wavelengths from 400-500 nm; PPF_(Red) is thePhotosynthetic photon flux for red wavelengths from 600-700 nm; andPF_(Red) is the Photon flux (photon count per second) for bluewavelengths from 600-700 nm.

FIG. 21 shows emission spectrum, normalized intensity versus wavelength(nm), for a grow-light Dev.13 (solid line—Dev.13) and absorptionspectra, normalized absorption versus wavelength (nm) for chlorophyll-a(dotted line—Chl-a). FIG. 22 shows emission spectrum, normalizedintensity versus wavelength (nm), for a grow-light Dev.14 (solidline—Dev.14). FIG. 23 shows emission spectrum, normalized intensityversus wavelength (nm), for a grow-light Dev.15 (solid line—Dev.15).

TABLE 10A Measured optical characteristics of solid-state grow-lightsDev. 13 to Dev. 16 Wavelengh range 400-700 nm 380-780 nm PPF₄₀₀₋₇₀₀ ¹PPE₄₀₀₋₇₀₀ ² PF₄₀₀₋₇₀₀ ³ PPF₃₈₀₋₇₈₀ ¹ PPE₃₈₀₋₇₈₀ ² PF₃₈₀₋₇₈₀ ³ (umol/s)(umol/J) (photon count/s) (umol/s) (umol/J) (photon count/s) Dev. 1342.148 1.7836 2.54 × 10²⁸ 48.049 2.0334 2.90 × 10²⁸ Dev. 14 42.8501.8063 2.58 × 10²⁸ 48.730 2.0541 2.94 × 10²⁸ Dev. 15 39.758 1.7352 2.39× 10²⁸ 48.769 2.1285 2.94 × 10²⁸ ¹PPF_(x-y) = Photosynthetic photon fluxfor wavelengths from x − y nm ²PEE_(x-y) = Photon flux Efficacy forwavelengths from x − y nm ³PF_(x-y) = Photon flux (photon count persecond) for wavelengths from x − y nm

TABLE 10B Measured optical characteristics of solid-state grow-lightsDev. 13 to Dev. 16 Wavelength range 400-500 nm (Blue) 600-700 nm (Red)PF_(Blue) ² PF_(Red) ⁴ Ratio Grow- PPF_(Blue) ¹ (photon PPF_(Red) ³(photon PF_(Blue): light (μmol/s) count/s) (μmol/s) count/s) PF_(Red)Dev. 13 23.362 1.41 × 10²⁸ 18.218 1.10 × 10²⁸ 1.28:1 Dev. 14 23.657 1.43× 10²⁸ 18.321 1.10 × 10²⁸ 1.29:1 Dev. 15 9.663 5.83 × 10²⁷ 29.215 1.76 ×10²⁸   1:3 ¹PPF_(Blue) = Photosynthetic photon flux for wavelengths from400-500 nm ²PF_(Blue) = Photon flux (photon count per second) forwavelengths from 400-500 nm ³PPF_(Red) = Photosynthetic photon flux forwavelengths from 600-700 nm ⁴PF_(Red) = Photon flux (photon count persecond) for wavelengths from 600-700 nm

As can be seen from TABLE 10A, grow-light Dev.13 has a photosyntheticphoton flux (PPF₄₀₀₋₇₀₀) of 42.148 μmol/s and a photosynthetic photonefficacy (PPE₄₀₀₋₇₀₀) of 1.7836 μmol/J. As can be seen from TABLE 10B,the ratio of the photon flux (photon count per second) in the blueregion (PF_(Blue)) to the photon flux (photon count per second) in thered region (PF_(Red)) is about 1.3:1 (1.28:1).

As can be seen from TABLE 10A, grow-light Dev.14 has a photosyntheticphoton flux (PPF₄₀₀₋₇₀₀) of 42.850 μmol/s and a photosynthetic photonefficacy (PPE₄₀₀₋₇₀₀) of 1.8063 μmol/J. As can be seen from TABLE 10B,the ratio of the photon flux (photon count per second) in the blueregion (PF_(Blue)) to the photon flux (photon count per second) in thered region (PF_(Red)) is about 1.3:1 (1.29:1).

As can be seen from TABLE 10A, grow-light Dev.15 has a photosyntheticphoton flux (PPF₄₀₀₋₇₀₀) of 39.758 μtmol/s and a photosynthetic photonefficacy (PPE₄₀₀₋₇₀₀) of 1.7352 μmol/J. As can be seen from TABLE 10B,the ratio of the photon flux (photon count per second) in the blueregion (PF_(Blue)) to the photon flux (photon count per second) in thered region (PF_(Red)) is about 1:3.

While the foregoing purple grow-lights have been described as utilizinga combination of one or more broadband blue light emitting devices andone or more broadband red light emitting device according to embodimentsof the invention, it will be understood that the invention alsoencompasses grow-lights comprising a combination of one or morenarrowband blue and one or more narrowband/broadband red light emittingdevices; and grow-lights comprising a combination of broadband fullspectrum blue light emitting devices and one or morenarrowband/broadband red light emitting devices.

ABBREVIATIONS

-   -   BBL—Black Body Locus    -   Blue Chl-a LED-Blue light emitting device—peak emission        wavelength matching chlorophyll-a (Chl-a) blue absorption peak    -   Blue Chl-b LED-Blue light emitting device—peak emission        wavelength matching the chlorophyll-b (Chl-b) blue absorption        peak    -   Caro—Carotenoid    -   CASN—Calcium Aluminum Silicon Nitride    -   Chl-a—Chlorophyll-a    -   Chl-b—chlorophyll-b    -   COB—Chip On Board    -   FWHM—Full Width at Half Maximum    -   LED—Light Emitting Diode    -   MQW—Multiple-Quantum-Well    -   PAR—Photosynthetically Active Radiation    -   PAS—Photosynthesis Action Spectrum    -   PC Red LED—Phosphor Converted Red LED    -   PF—Photon Flux    -   PF_(x-y)—Photon flux for wavelengths from x-y nm    -   PFD—Photon Flux Density    -   PPE—Photosynthetic Photon Efficacy (Kp)    -   PPF—Photosynthetic Photon Flux    -   PPF_(x-y)—Photosynthetic Photon Flux for wavelengths from x-y nm    -   Red Chl LED-Red light emitting device—peak emission wavelength        substantially matching the chlorophyll red absorption peaks    -   SPD—Spectral Power Distribution    -   YAG—Yttrium Aluminum Garnet

REFERENCE NUMERALS

-   -   10 a Chlorophyll-a (Chl-a) blue absorption peak    -   10 b Chlorophyll-a (Chl-a) red absorption peak    -   20 a Chlorophyll-b (Chl-b) blue absorption peak    -   20 b Chlorophyll-b (Chl-b) red absorption peak    -   30 a, 30 b Carotenoid (Caro) blue absorption peaks    -   40 Photosynthesis Action Spectrum (PAS) blue peak    -   50 Photosynthesis Action Spectrum (PAS) red peak    -   100 Light emitting device    -   110 Package    -   112 Package base    -   114 Package side wall    -   116 Cavity    -   118 LED chip    -   120 Bond wire    -   122 Contact pad    -   124 Light transmissive material    -   200 Grow-light    -   210 Substrate    -   220 Light emitting device    -   220 a Blue Chl-a LED    -   220 b Blue Chl-b LED    -   220 r Red Chl LED    -   240 Blue emission peak

What is claimed is:
 1. A grow-light comprising: a first solid-statelight source that generates blue light with a blue photon flux; and asecond solid-state light source that generates red light with a redphoton flux; wherein a ratio of the blue photon flux to red photon fluxis from about 1:3 to about 3:1.
 2. The grow-light of claim 1, whereinthe ratio of the blue photon flux to the red photon flux is selectedfrom the group consisting of: about 1:1, about 3:1, and about 1:3. 3.The grow-light of claim 1, wherein the first solid-state light sourcegenerates blue light with a maximum intensity wavelength of at least oneof: from 420 nm to 460 nm; from 460 nm to 480 nm; and from 450 nm to 465nm and 480 nm to 495 nm.
 4. The grow-light of claim 3, wherein the firstsolid-state light source comprises a plurality of narrowband blue LEDsfor generating a plurality of different maximum intensity wavelengthnarrowband blue light emissions.
 5. The grow-light of claim 1, whereinthe first solid-state light source comprises a broadband solid-statelight source that generates broadband blue light with a maximumintensity wavelength from 420 nm to 495 nm and a full width at halfmaximum of at least 30 nm.
 6. The grow-light of claim 1, wherein thefirst solid-state light source generates a first broadband blue lightwith a maximum intensity wavelength from 420 nm to 450 nm with a firstblue photon flux, and a second broadband blue light with a maximumintensity wavelength from 460 nm to 470 nm with a second blue photonflux, and wherein a ratio of the first blue photon flux to the secondblue photon flux is from about 2:1 to about 4:1.
 7. The grow-light ofclaim 1, wherein the second solid-state light source comprises anarrowband blue LED and a red photoluminescence material.
 8. Thegrow-light of claim 1, further comprising a red solid-state light sourceor a photoluminescence material that generates red light with a maximumintensity wavelength from about 680 nm to about 780 nm.
 9. Thegrow-light of claim 1, wherein the blue light has a full width at halfmaximum of at least one of: at least 40 nm; at least 50 nm; at least 60nm; and from 40 nm to 80 nm.
 10. A grow-light comprising: a solid-statelight source that generates blue light with a maximum intensitywavelength from 400 nm to 520 nm with a spectrum whose emissionintensity varies over a wavelength range of at least 40 nm by: less than25%; less than 15%; or less than 10%.
 11. The grow-light of claim 10,wherein the emission intensity varies by less than 10% from 430 nm to470 nm or from 440 nm to 465 nm.
 12. The grow-light of claim 10, whereinthe solid-state light source comprises: a plurality of narrowband LEDsfor generating a plurality of different maximum intensity wavelengthnarrowband blue light emissions or a plurality of broadband blue LEDsthat each generate a broadband blue emission with a maximum intensitywavelength from 400 nm to 520 nm.
 13. The grow-light of claim 10,further comprising a red solid-state light source or a redphotoluminescence material that generates red light with a maximumintensity wavelength from 630 nm to 700 nm.
 14. A grow-light comprising:a broadband solid-state light source that generates broadband blue lightwith a maximum intensity wavelength from 420 nm to 495 nm and a fullwidth at half maximum of at least 30 nm.
 15. The grow-light of claim 14,wherein the maximum intensity wavelength of the broadband blue light isat least one of: from 420 nm to 450 nm; from 460 nm to 480 nm; and from450 nm to 465 nm and 480 nm to 495 nm.
 16. The grow-light of claim 14,wherein the broadband solid-state light source comprises a plurality ofnarrowband blue LEDs for generating a plurality of different wavelengthnarrowband blue light emissions.
 17. The grow-light of claim 14, furthercomprising a red solid-state light source or a red photoluminescencematerial that generates red light with a maximum intensity wavelengthfrom 630 nm to 680 nm.
 18. The grow-light of claim 14, furthercomprising a red solid-state light source or a photoluminescencematerial that generates red light with a maximum intensity wavelengthfrom about 630 nm to about 780 nm.
 19. The grow-light of claim 14,further comprising at least one of: a green to yellow photoluminescencematerial that generates green to yellow light with a maximum intensitywavelength from about 540 nm to about 600 nm; and cyan to redphotoluminescence material that generates cyan to red light with amaximum intensity wavelength from about 500 nm to about 680 nm.
 20. Thegrow-light of claim 19, wherein the grow-light generates light with amaximum intensity wavelength from 400 nm to 520 nm with a spectrum whoseemission intensity varies by: less than 25% over a wavelength range ofat least 40 nm; less than 20% over a wavelength range of at least 40 nm;less than 15% over a wavelength range of at least 40 nm; less than 10%over a wavelength range of at least 40 nm; or less than 10% from 430 nmto 470 nm or from 450 nm to 465 nm.